Telephone-exchange system



E. E. CLEMENT TELEPHONE EXCHANGE SYSTEM Filed April 15, 1905 '7 Sheets-Sheet 1 E. E. CLEMENT I TELEPHONE EXCHANGE SYSTEM May 25 Filed A ril 15, 1905 '7 Sheets-Sheet 2 E. E. CLEMENT TELEPHONE EXCHANGE SYSTEM Filed April 15, 1905 7 Sheets-Sheet 5 May 25 1926. E. E. CLEMENT TELEPHONE EXCHANGE SYSTEM 7 Sheets-Sheet 4 Filed April 15, 1905 May 25 1926.

E. E. CLEMENT TELEPHONE EXG HANGE SYSTEM Filed April 1905 7 Sheets-Sheet 6 wanna May 25 1926. 1,585,769

E. .E. CLEMENT TELEPHONE EXCHANGE SYSTEM Filed April 1905 7 Sheets-Sheet 7 MULTIPLEJA c/rs A/VWE/f/NGJA c/rs Invgntot Patented May 25, 1926.

, warren STATES FATEN'I' QQL FEQE.

EDWARD E. CLEMENT, OF WASHINGTON, DISTRICT OF COLUMBIA, ASSIGNOR, BY MESNE ASSIGNMENTS, TO THE NORTH ELECTRIC MANUFACTURING COMPANY.

TELEPHONE-EXCHANGE SYSTEM.

Application filed. April 15, 1905.

My invention relates to telephone exchange systems, and has for its object the production of such a system which shall be highly ellicient and economical in operation and maintenance. I may designate my system generally as a clearing house system, that is, I provide a main central exchange with trunk lines runningto branch exchanges, and at the branch exchanges I install automatic switching apparatus of a peculiar kind. The subscribers lines radiate from the branch exchanges, and the subscribersinstruments are simple telephone sets the same as used in any manual. system, without any complication whatever. I shall describe the system as full, common battery, with double supervision at central. provision for recall, and all the time and labor-saving contrivances which belong to a modern manual system. The most noticeable feature is the location of all operators at the main central exchange or clearing house, and the provision I make for the uniform distribution of the entire exchange load or rather of the loads of all the branch exchanges among all the operators. T his is accomplished by bringing in the trunks from each branch exchange and instead of landing them all for answering purposes before a particular operator at one position, or one section, I distribute them uniformly among all the operators. The effect of this is that no matter what fluctuation occurs, in what branch exchange, it affects all the operators, and this is particularly so because I make provision for reversing the distribution so to speak, or arranging it in echelon, so to speak, the subscribers moreover, selecting idle trunks, so that the subscribers at each branch exchange do the distributing unconsciously. The number of automatic switches at each branch exchange is less than the number of lines. lVhen a line calls it gets on a control circuit which applies cur rent. to and starts the first idle trunk switch to connect that switch with the calling line. According to one form of the invention, the trunks may be two way, each provided with a pair of automatic switches at the branch exchange, and according to another form they are one way, one-half of them, or whatever other proportion is required, being for incomingbusiness, and the rest for outgoing Serial No. 255,830.

business, the terminal switches being built and connected accordingly.

In order that the number of trunks in a large city .may be economiz-ed as much as possible, and with the knowledge that the fluctuations in load vary definitely according to the character of the subscribers line, it is part of my invention to arrange for relief trunks. That is, I run a body of trunk lines, embracing part or all of a trunk cable, to and through. one branch exchange to another one. Suppose the first exchange is in a business district, and the second is in a residence district; the peak of the load curve in the former is between eleven and twelve oclocl; in the morning, with a some what shorter horn early in the afternoon, while the peak of the load in the residence district is after the close of business hours. By combining two branch exchanges (or for that matter, as many as economy dictates), the trunks may be used at a high percentage of eliiciency during a longer period and with less less from idleness of investment than if two sets were used. In a city like New York, a single main cable might be run from a downtown exchange up the island to a point above Harlem, or even farther, with anywhere from two to twelve exchanges, taking oil multiple taps, to the main otiice which might be located anywhere along the main body, or at the large end of the cable. All connections will be made in this main oilice, and I can conceive of no greater means of economy in every respect tha this combination of a centralized working force under a single management, and a reduced cable system with the numerous elements i. 0., the subscribers lines. reduced to short lengths. Approximate estimates show that a ig of at least ten per cent in operating expenses is thus effected, and an enormous saving in cable, the latter, whether or no the relief or mutiple tap system is used. In using the latter, I prefer to have certain wires in the cable allotted to each branch exchange during specified hours, and shifting this allotment as the load shifts. Thus, pairs Nos. 211% to 2210 might be allotted to a business exchange until four p. m., and thereafter be taken up by a residence exchange. I consider myself to be the originator of every feature of this and all other arrangements, cir:

cuits, methods, and apparatus, herein set forth. and I shall claim all the same broadly and s zccil'ically.

I am aware that it is objected that in trunking to a central oilico from an automatic branch exchange the operators may not not know who is calling, as they would in a plain manual system, but I consider this an adi'ant: gc, it positively does away with favoritism. in my system, a subscriber calling a dozen times in succession is liable to come in on as many different positions, over as many cill'erent trunks, and in a large exchange or clearing house the operators would get a very shifty and shifting chance for acquaintanceship.

My invention is illustrated in the accompanying drawings, wherein Figure 1 shows the subscribers station terminating in the multiple contacts of a trunk connector switch at a sub-exchange or station, also the sub-exchange end of the central oflice trunk, to which is connected the connector switch. The trunk to central oilice in this case is a. single-way trunk. Figure 2 is a similar diagram showing the central oliice ends of two trunks, one being used for incoming calls, while the other is used for outgoing calls. The cord-circuit is also shown, which forms the connecting link between these trunks. Figure 3 shows the outgoing end of a trunk at the sub-exchange, also the sub scribers line apparatus at sub-station. F igure 4 shows the subscribers station terminating in multiple contacts of two trunk connector switches, both of these switches being connected to the trunk, one, being the active switch for outgoing calls, the other being the idle switch used for incoming calls. Figure 5 shows the central ofiice end of two two-way trunks, one being used to illustrate an incoming call, the other for an outgoing call. The cord-circuit is also shown, which serves as the connecting link between these two trunks. Figure 6 is a duplication of Figure & and is used in illustrating a two-way trunk being used for an outgoing call; Figure l illustrating a twoway trunk being used for an incoming call. The apparatus and the wiring in several of the figures being identical, the same lettering is observed throughout. Figure 7 is a diagram illustrating the distributing scheme. for a clearing-house system. Figure 8 is a portion of a diagram illustrating the row and individual wipers of the line finder switches.

The scheme shown in Figures 4, 5 and 6 is a combination of the incoming and outgoing trunks shown in Figures 1, 2 and 3. In the latterv I have shown two trunks, one being used as an outgoing trunk and the other as an incoming trunk. In Figures 4-, 5 and 6 I have combined the two switches in one trunk so that the same trunk may be used for both incoming and outgoing calls. This change is made without altering the wiring or apparatus in the least, with the exception of adding three contact springs, 2 2 and .2 to the outgoing switch to be operated by the spindle.

in describing Figures 4, 5 and (3 it will not be necessary to describe Figures 1, 2 and 3, as the operation is identical in each case.

Referring now to Figure l, A is the subscribers station, equipped with apparatus usual in common battery systems. it consists oi a transmitter T, receiver R, hool; H, ringer Q and condenser L. The linewires 1 and 2 from this station terminate in multiple contacts .2 and .2 in the idle connector switch and in the multiple terminals 2 and 2 of the active connector switch Z. The line apparatus controlling these switches consists ot the l'ollowing: line relay M, retardation coil N, cut-oil rcluy S. The line relay M is connected to the line wire 1 by the wire 3, the other terminal being grounded. The contact m makes a momentary connection with the contact m when the relay M is energized. This inomentary connection is made to start the idle switch Z. The contacts or in all the line relays are connected by the common wire 10. This common wire 10 in part forms the starting circuit of the idle switches for all the lines in each exchange or group. Contact 922* is grounded through the contacts 8 and s of the relay S, and when this relay is energized these contacts are broken, as is necessary for an outgoing call to prevent the switch from operating upon the relay M becoming energized when the called subscriber answers. The common wire 10 is connected to the starting relay S in the connector switch Z by the following path: wire 1'7, contacts 2 and .2 wire 24;, contacts 2 and 2 wire 2-10, contact a winding of the relay S to battery. One terminal of the relay S is connected to the 1nultiple terminals 2 and 2 the other terminal being grounded. The contact a of the relay S is connected to the row contact .2 and contact 8 to the individual contact a. The contact 3 is connected to the wiper of the connector switch Z by the wire 9 and also to the contact m of the relay ill by the wire 6. The retardation coil F is connected to the wire 2 by the wire at, the other terminal being connected to battery by the wire 5. The row contact a affords a means for stopping the connector switch Z on the desired row of terminals in which the calling line is located, while the individual contact 2 forms a means for stop-- ping the wipers of the switch Z on the contacts ot the line calling. The idle connector switch circuit Z includes the following: starting relay S and relay S which con trol the side switches X and X, the vertical magnet l rotary magnet F, release magnet Vi", interrupting machine G, spindle a, on which are mounted the trunk wipers a, a, row wiper .2 individual wiper .2 and wiper a for operating the cut-o'tl relays S and S and the wiper 2 which jointly Controls the release magnet One termi nal oi the relay S is connected to the common starting wire 10 by the path already described, the other terminal being connected to battery. One terminal of the relay S is connected to the wipers s and 2 by the wire 21, the other terminal being connected to battery by the wire 30. The contact s of the relay S is connected to the blade of the switch X by wire 26. One terminal of the vertical magnet F is con nected to the contact 5 ot the relay S by the wire 29, the other terminal being connccted to the first point in the side switch X by the wire 27, one terminal of the rotary magnet F is also connected to the contact a by the wire 29, the other terminal being connected to the second point in the side switch X by wire 28. The contact .9 of the rela S is connected to the blade of the switch X by wire 31, while the contacts a and s are connected to the bus-wires leading to the interrupting machine G. One terminal of the release magnet W is connected to the contact spring a by wire. 32, the otl or terminal being connected to battery. The contact 10 is connected to the relay S by the wires 23 and 21, contact to being grounded.

Contacts w and e when in connection at the end of a conversation, energize the relay S and restore the side switches X and X to their normal or starting position. The active connector switch Z can be in the form of any standard switch responding to the vertical and rotary impulses of a transmitter or sei'iding device. In this case, for illustration I have shown the switcl commonly known as the Strowger, which is illustrated and described as to its mechanical "features in U. S. Letters Patent to Keith and Erickson No. 815,176 dated March 13, 1.906. This circuit comprises the following: vertical relay S rotary relay S; test relay X; ringing relay Y; vertical magnet 8 rotary magnet a; release magnet lV and side. switches a, 2 s and a. In addition to the foregoing T have added a cut-off relay 8' for the purpose oi cutting oil the vertical and rotary relays and shortcircuiting the condensers when the trunk is being used. I have also added the wiper .2 for controlling the cut-oil relay S and the wiper a for controlling the cut-olt relay E of the line circuit for reasons which will be shown later. I have also added springs .2 a and a controlled by the spindle These springs are arranged in series with the corresponding springs of the svitch Z controlled by the spindle tor the purpose of cutting 0d the idle switch when it is in use and cutting on the next succeeding idle switch.

Referring now to Figure 5, the central office end of the trunk from the sub-station terminates in the springs j and 3', respectively, of the jack J. The trunking apparatus consists of the signal relay M, one terminal of which is connected to the trunk wire 20 by the Wire 35, the other terminal being grounded through the wire 86, contacts m and n of the cut-off relay N. The relay M jointly controls the busy lamp a and directly controls the signal lamp m One terminal of the cut-oil relay N is connected to the thimble j of the jack J by the wire 89. The relay N jointly controls the busy lamp a and disconnects the'signal relay M when energized. I have thus described the central oiiice end of the incom ing trunk, and as the central oilice end of the outgoing trunk is identical it will need no description. The cord-circuit consists of the following: the answering plug P, calling plug P, supervisory relay S retardation coil I, controlling relay S", answering supervisory lamp 8 calling supervisory relay S retardation coil 1, controlling relay S calling supervisory lamp 8 and the automatic trunk discon necting relay if. The tip 3) of the answering plug P is connected to the tip j) of the calling plug P by the following path: strand a l, condenser L, contacts 76, 0t key K, strand 4L6; sleeve p of the answering plug 1 connected to the sleeve 9 of the calling plug P by the following path: strand 45, condenser L, contacts 7a", 3 of key K and strand -l7. Relay S is connected to the strand H by the wire -18 and to ground by the wires and 66. One terminal ot' the retardation coil 1 is connected to the. strand e5 by the wire 49, the other terminal connected to ground by the wires and 66. Contact s of the relay 5) is connected to the supervisory lamp a and. to the contact .9 of the. relay S by the wire til and from there to battery through the contact a and the wire (50.- The rontact a is connected to one terminal of the relay 5 and the contact .9 the other terminal of the relay S being connected to one terminal of the lamp 5 and contact 5 of the relay S by the wires 5? and Contact 3 of the relay S is connected to the strand 46 by the wires 62 and 50, and the contact 8 is connected to the strand 4'1. The contact 8 is connected to battery by the wires and 60. One terminal of the relay S is connected to the strand 4E6 by the wire 50, the other terminal being connected to ground by the wires 67 and 61- One terminal of the retardation coil 1 isconnected to the strand 47 by the wire 51, the other terminal being connected to ground by the wires 67 and 64:. One terminal of the relay S is connected to the third conductor 72 of the calling-plug P by the wire 65, the other terminal and contact being grounded.

Figure 6 being identical with Figure 4 will need no description, but the operation will be explained in thproper order.

The operation of my system is as follows: Referring now to Figure 4:, the subscriber taking down his receiver closes the circuit of the line relay M, which attracts its armatures and a passing ground is placed on the common wire 10, wiich affects the starting relay S in the idle connector switch Z by the following path: ground, contacts a, s of the relay S, wire 8, contacts m m of the relay M, common wire 10, wire 17, contacts 2 .2 of the connector switch Z, wire 2%, contacts 2 e of the active connector switch Z, wire 24-0, relay S to battery. The relay C being now energized attracts its armatures and connects the interrupting machine G to the vertical magnet F through the first contact in the side switch X. The vertical magnet F now operating causes the spindle a carrying the wipers, to step in a vertical direction until the wipers come to rest on the row containing the multiple contacts of the calling line. The wipers come to rest in the desired row on account of the ground being placed on the row contact by the relay M when it first became energized. This ground is traced by the following path: row contact .2 wire 12, contacts 8 and s of the relay S, wire 9, wire 6, contacts m and m of the relay M to ground. Ground is also placed on tne individual contact 2 at the same instant and by the same relay. These contacts, the spindle .2, the vertical and rotary magnets F and F and the wipers are all shown as to their mechanical a rangement in Figure 8. As shown in this figure, the row contacts are arranged in a single vertical row, in order that the proper level may be selected, and the individual contacts are arranged with a number of them, as ten, in each row or corresponding to each level. As soon as the wiper .2 comes in contact with the terminal .2 the relay S which controls the side switches X and X, is energized, causing the side switches to take one step. This one step cuts off vertical magnet F and cuts on in its place the rotary magnet F. Under the influence of this magnet the spindle .2, carrying the wipers, begins to rotate and continues to rotate until the individual wiper 2 comes into contact with the terminal 2 The relay S is then energized the second time, the side switch makes one more movement, which disconnects the rotary magnet IF and at the same time releases the relay S' by disconnecting the ground from the contact 8, which was at that time in connection with the contact 8 leading through the winding to battery. The wipers now resting on the contacts of the line which originated the call, the wiper 2 to which is connected the cut-off relay S connects with the contact 2 which encrgizes the cut-oti' relay S, which upon attracting its armatures disconnects the ground or busy signal from the row wiper .2 and the individual wiper 2 by breaking the contacts 8 s", s and The contacts 8 and s are also broken for use in outgoing calls which disconnect the ground from the contact m of the relay M to prevent the starting circuit being closed when the called subscriber answers. The wiper a, which jointly controls the release magnet \V, is now connected to the contact 2 leading to the contact m of the relay M. The release magnet TV is now placed under the control of the line relay and is energized when the calling subscriber hangs up his telephone. The spindle z, in making its first vertical movement, disconnected the starting relay S by breaking the contacts 2 and 2 The relay S being disconnected from the common wire 10 cannot be energized by any other line relay until at the end of the conversation, when the contacts 2 2 are again connected. At the first movement of the spindle 2 the contacts .2 and 2 were closed, which cut on the next idle switch to the wire 10 by the following path: wire 17, contacts 2 and .2 wire wire 14 to the next idle switch. The contacts .2 and .2 were also closed at the same time, which connected the release magnet \V to the wiper z. The wiper 2 to which is connected the cut-off relay S of the active switch Z being now connected to the contact Z leading to the winding of relay S, said relay S becomes energized, attracts its armatures, cuts off the vertical and rotary relays S and S, respectively, short-circuiting the condensers L and L The calling subscriber is now connected to the clearing-house or central ofiice through the trunk wires 19 and 20. This connection being completed, the signal relay M is placed in series with the rctarda tion coil N, Figure it, by the following path: battery B, wires 18 and 5, N, wires at and 2, contact .2 wiper .2 wires 90 and 5-5.3, hi, wire 36, contacts a and a of the relay N to ground. The relay M thereupon becomes energized attracting its armaturcs, causing the signal lamp 772 to glow by closing the contacts at and m The busy lamp n is also caused to glow by closing the contacts m and m. This busy lamp n and the jack J are multipled in each position. The operator upon perceiving the line signal inserts the answering plug P into the jack J, causing battery to How to the relay S and the cutoff relay N in series by the following path: ground, S", wire 56, 79 7' wire 39, N, wires 42 and to battery. The relay N becoming energized attracts its armature, disconnects the relay M by breaking the contacts a and n extinguishing the line lamp m The contacts a and a are closed causing the busy lamp n to continue glowing notifying other operators that this particular trunk is busy. The relay S being in multiple with the line relay M, Figure l, is energized, attracts its armatures breaking the contacts 8 and s preventing the lamp 8 from glowing as this lamp circuit was completed by the closing of the contacts of the relay S. The operator upon finding the number desired inserts the calling plug P into a trunk J" leading to a connector switch,

in a sub-exchange containing the multiple contact of the line desired. This insertion causes current to flow through the relay S and the relay N, in series, by the following path: ground, S, wire 65, p j wire 105, N wire 106 to battery. The relay N becom ing energized attracts its armature, disconnects the line relay l 2 and at the same time closes the contact leading to the busy lamp 1?, causing it and its multiple lamps in the other positions to glow, notifying the operators that this trunk is busy. The relay S becoming energized attracts its armatures, causing the lamp 8 to glow, which continues to glow until the called subscriber answers. The operator upon placing the calling plug P into the trunk jack J throws the lever of her key K into contact with the dial or automatic sender, which can he of any standard form, transmitting impulses affecting the vertical and rotary relays and the active connector switch. The operator will only have to manipulate her sender twice, the first time to transmit the ten numeral of the line wanted and the second time the unit numeral of the line wanted, having previously learned from the subscriber the thousand and hundred numerals of the line wanted. In operating her sender the first time impulses are sent over the trunk wire 70, to the vertical relay S in the connector switch Z" at the sub-station, Figure 6. These impulses corresponding to the ten numeral of the line wanted affect the relay S correspodingly, which attracting its armature operates the vertical magnet s by the following path: ground, contacts s 8 wire 93, contacts in, m of the relay X, wire 94, side switch 2 vertical magnet s wires 90, 86 and 18 to battery. Magnet 3 in operating causes the spindle 2 carrying the wipers to step up vertically to the row in which the wanted line is located. After the last impulse has come in over the wire 70, one impulse is sent in over the wire 71, afiecting the relay 8".

This relay attracting its armature energizes the relay X causing the side switches 2 2 2 and 2 to make one step, cutting 0d the vertical magnet s and in its place cutting on the rotary magnet 8 It "21150. .9011

the wiper s to the magnet W through the side switch 2, wires 92 and 96 and contacts 02 and :0 of the relay X when it is energized. The sender in being operated the second time transmits impulses over trunk wire 70, affecting the relay S which now in turn operates the rotary magnet s. This magnet in operating causes the spindle 2 to rotate and carry the wipers opposite to the contacts leading to the desired line. After the last impulse has been sent in over the trunk wire 70, one impulse is sent over the trunk wire 71 aifecting the relay S", which operates the relay X the second time. The relay X causes the side switches to make one more step which disconnects the rotary magnet .9 through the side switch 2 grounds the wiper 2 through the side switch 2 and connects the wire 72 to the wiper e by the following path: contacts a, a of the relay Y, wire Tt, side switch 2 wire 76 to wiper 2 It also connects the wire 73 to the wiper 2 by the following path: contacts .2 2" of the relay Y, wire 7 5, side switch 2 wire 77, to wiper 2 The last movement of the side switch 2 cuts on the ringing relay Y and. places it under control of the vertical relay S by the following path: battery B, wires 18, 86, 90, Y, side switch a, wire 94, contacts a m of the relay X, wire 93, contacts 8 s to ground. The trunk wipers now resting on the contacts of the desired line, the operator pushes the ringing button which closes the circuit of the relay S over the trunk wire as follows: battery to key K, wire 70, 78, s 8 79, S and ground.

This relay being operated closes the circuit of relay Y, which attracting its armatureopens the wires T l, 72, 7 5 and 73, and generator current is sent out through the wipers 2 and .2 to the line of the called subscriber. Spindle 2 making its first vertical step breaks the contacts a and 2 which disconnects its mate idle switch from the starting circuit 10 at the same time the contacts 2 and 2" were closed, which cuts on the next succeeding idle switch to the starting circuit 10. The wiper 2 now being in connection with the contact 2 the cut oil relay S in the line circuit is energized, and attracting its armature disconnects ground from the contact m of the relay M by breaking the contacts a and s". This is to prevent the relay M, when energized, from starting one of the idle switches. The contacts s and s are also broken to prevent ground being placed on the row contact 2 and the individual contact 2. The cut-off relay S is connected to the wiper 2 which now being in connection with the contact 2 leading to the contact m? of the relay M places it under control of that relay. The called subscriber upon answering energizes the relay which upon attracting its armatr-res r ats th r lay w ich l 9. 1 9

the vertical and rotary relays S S respectively, and short circuits the condensers and L. The called subscriber is new connected straight through to the clearing-house over line wire 1 by the tollo ring path: side switch wire 7%, contacts and 2, wires 72, 83, contacts 3 a oi the relay S wires 78 and 70 to 7' of l e jacl: Figure :3; and

l e li over No. 2 side of t no by the following "II 20 sit ,nne

path: .2, 2 wire to switch .4 75, contacts 2 2 .rires s, 84, contacts a, 8 of the relay S wires 81 and 71 to j of the jack J, Eigure Relay E5 Figure 5, being in multiple with. the line relay M, Figure (5, of the called subscribcfs line, hecomes n vrgized when he takes down his receiver, which extinguishes the lamp 8 notifying the operator at the clearinghouse that the call is answered. At the end of the conversation the calling subscriber hanging up his telephone opens the line-circuit 12, which deonergizes the line relay M, closing the contacts on, m. The circuit of the release magnet V is closed and upon attracting its armatures it releases the switch Z, and all parts are returned to their normal or starting position and the switch again connected to the starting circuit 10. The wiper 2 leaving the contact 2 opens the circuit of the relay S which removes the short-circuit from the condensers and again connects the vertical and rotary relays ot the active connnztor switch Z.

Referring now to Figure 5, relay 5" also becomes dcencrgized and the circuit of the lamp 8 is closed, causing it to glow, notifying the operator that the calling subscriber has hung up his telephone. The contacts 8 s are now closed and the relay Q7 ias its circuit partly completed. The

k) called subscriber in hanging up his telephone opens the circuit of the line relay M, Figure 6, which breaks the contacts m and or", releasing the cut-oil relay S in the active connector switch 75, which removes the short-circuit from the condenser." and again connects the vertical and rotary relays S and S. The relay S Figure 5, also be comes dcenergized when the called sub scriber hangs up his telephone, and its armature falling back closes the contacts a, a", causing the lamp .9 to glow. At the same time the closing of the contacts 8 8 coin pletes the circuit of relay S The relay S becoming energized attracts its armature and connects battery to the vertical and rotary relays S and S, Figure 6, by the following paths: battery B, wires 60 and 59, contacts a 3 wires 62, 50, strand 16,1),- j, wires 70, 78, contacts 5 s of the relay S Figure 6, wire 79, S wire 80 to ground; and from battery B, wires 60, contacts 8 wires 58, 51, strand 47, p, 7", wires 71, 81, contacts a of the relay .53 Fig ure 6, wire 82, S, wire 80 to ground. Both relays S and S are energized simultaneous ly over both sides of the trunk by battery to ground, and attracting their ari'natures close he contacts 8 and s, completing the circuit of the release magnet XV, which becoming energized restores the connector switch Z'" to its normal position, the spin dle in falling closing the contacts 2 and .2 putting its mate idle switch Z back on the starting circuit 10. The relay S Figure 5, remains energized or locked through the contacts 8 and s of the relay S by the following path: battery, wires and contacts a, a, winding of the relay S wires 57, (33, contacts a, s of the relay S to ground. It will be seen that the battery being placed on the strand 46, relay S be comes energized, attracts its armatures, breaks the contacts 5 s and would extinguish the lamp 8 This contingency is provided for by the terminal of the lamp leading to the contact a, being connected to battery by another path as follows: wire 61, con tacts 8 a of relay S wire 53, contacts 3 and s of relay S wires 59 and 60 to battery. The operator upon seeing both lamps glowing withdraws the plugs from the jacks and the relays S and S become de energized; relay S disconnecting the lamp a and the relay S releasing the relay S, which in turn cntinguishcs the lamp 8 and releases the relay S.

In the foregoing description I hare shown two two-way trunks both being identical, one being used as an incoming trunk and the other as an outgoing trunk, so it follows that each trunk may be sed either for an incoming or an outgoing call as the case may be. In Figures 1, :2, and 3 the trunks are shown as single trunks, that is the trunk shown in Figure 1 can only be used for incon ing calls, while the trunk shown in ure 3 can only be used for outgoing calls, and in the central otlice end of the outgoing trunk, Figure 2, the line relay and signal lamp are of course on itted. 7

Referring now to Figure 7, I have shown diagramnjiatically the, distril'iutinp scheme as applied to the clearing-house system. A, B, C and D represent tour sub or branch exchanges with trunk lines connected to the -house. Jr, B, C and D represent clcariii, groups of trunlis from their respective stations. (1 (4 a, etc, b, 6 11*. etc., 0, 0, 0 etc, ll, (Z (Z", etc., represent these groups of trunl-zs being distributed to the answering jacks at the various operators positions, 2, 3, l, 6, etc. It will he noticed that the trunks from each sub-station are distributed equally among the various operators positions at the clearing-house, so that the load at all times is practically uniform at all positions. A", B C and D represent the diti'erent groups of trunks from the sub-exchanges being carried to multiple jacks in the sections 1, 2, 3, each group being multipled in each section so as to be in reach of any operator to be used for outgoing busi ness. By this method of distribution no one operator will be overburdened with work, while anoth r operator is idle, and besides no girl can tell from her line-signal the number of the line calling, that is the number oi the subscribefs telephone, as his signal. may come in on any trunk from the sub-excl'iange and to pick out a dil'lerent girl at each call. Thus it will be seen that the operator an show no favoritism to the calling subscriber by giving his call preference over others.

Having thus described my invention what I claim and desire to secure by Letters Patent .is

1. In a telephone system, a plurality of telephone lines, a plurality of trunks, Y- switches, one associated with each of said trunks and each adapted to connect its associated trunk to a calling one of said telephone lines, line controlled relays associated with said telephone lines, and a motor circuit extending from one of said Y-switches and branching in multiple to contacts of said line relays whereby, when any line is calling, said motor circuit will be closed by the line relay contact of the calling line, causing the motor mechanism of said Y-switch to operate.

2. In a telephone system, a plurality of telephone lines, a plurality of trunks; Y- switches, one associated with each of said trunks and each adapted to connect its associated trunk to a calling one of said telephone li es, line controlled relays associated with said telephone lines, a motor circuit extending from a predetermined Y -switch and l'n'anching in multiple to contacts of said lino relays, whereby, when any line is calling said motor circuit will be closed by a line relay contact of the calling line causing the motor mechanism of the predetermined Yswitch to operate, and means in the operating Y-switch to extend said motor circuit to the motor mechanism of another Y- switch when the operating if-switch connects with the calling line, substantially as described.

3. In a telephone system, a plurality ottelephone lines, a plurality of trunks; Y- switches, one associated with each of said trunks and each adapted to connect its associated trunk to a calling one of said tele phone lines, line controlled relays associated with said telephone lines, a motor circuit extending from one of. said Y-switches and branching in multiple to contacts of said line relays, whereby, when any line is calling said motor circuit will be closed by a line relay contact of the calling line causing the motor mechanisn' of said Y-switch to operate, and means in each Y-switch for removing its motor mechanism from said motor circuit when the (switch is busy, substantially as described.

An exchange system comprising a cen tral station, telephone lines extending thereto, switching mechanisms to which the lines are connected, a unitary device individual to each line at the central station for controling any one of its switching mechanis is, and means individual to each switch ing mechanism "for transferring the line control from it to another switching mechanism.

An exchange s *stem comprising telephone lines. switching mechanisms to a plurality of which each oi? the lines is connected, each switching mechanism including a plurality of sets of fixed contacts and a set of movable contacts adapted in its travel to successively engage the sets of fixed contacts,-

starting means associated with each switching mechanism, and line controlled means individual to each line adapted to directly control the starting means 01 any one of the switching mechanisms to which the line is connected.

6. In a telephone exchange system, a plurality of line circuits, link circuits for interconnecting the lines, and primary selector switches for connecting calling lines with said links, each of these switches containing terminals of the lines divided into groups, testing contacts associated with the several groups, a test wiper tor the group or row test contacts, means for driving a switch in response to a call over any one of the lines represented in its banks, so as to impel its test wiper over the row test contacts, means adapted to stop the switch when the test wiper rests upon the test contact associated with the group or row of individual contacts in which a contact of the calling line appears, and means thereupon becoming effective to drive the switch into connection with the indi idual contacts of the line calling. a

7. In an exchange system, a plurality of circuits to be selected, and a testing selector switch containing testing contacts forming terminals of said circuits, arranged in successive groups or rows, and a common test contact associated with each group, test wipers and means for actuating the switch with two motions for grou 3s and individual se ection, together with means responsive to the test on the group contacts, for shifting the motion from group selection to individual contact selection.

8. In a telephone exchange system, a plurality of circuits and a two motion selector switch containing terminals thereof arranged in parallel rows, and means for ac tuating the co-operating switch terminals so as to test first for a group or row and then for an individual contact in the row.

9. Ira telephone exchange system, a testin selector switch comprising the following instrumentalities: a cont-act bank containing a plurality of rows of terminals, an associated set of test terminals, comprising one test tern'iinal for each row, a spindle carrying wip rs adapted to co-operate with the individual contacts in the rows and with the associated row contacts, actuating magnets tor the spindle, and circuits for said magnets automatically controlled in the operation of the wipers.

10. in a telephone exchange system, a pinrality of circuits to be selected, and a testing selector switch COll'lpllSiDg the following instrumcntalities: a contact bank containing a plurality of rows of terminals connected to said circuits, an associated set of test terminals, comprising one test terminal for each row. a spindle with a pair of test wipers and a pair of connecting wipers, one of said test wipers adapted to co-operate with the row test contacts and another with the individual test contacts in each row, means for imparting motion to the spindle so as to move therow test wiper over the row contacts, means for imparting motion to the spindle so as to move the individual test wiper over the individual test contacts in any selected row, and a shifting device responsive to the row test, and adapted when energized to de prive the first n'iotor-means of energy, shifting the same to the second motor-means, whereby identification and connection through the connecting wipers of a particular circuit is attained automatically by first segregating the row and then the individual location in the row.

11. In a telephone exchange system, line circuits, line relays therefor, a primary selector switch containing connective terminals in rows connected to the line circuits, individual test contacts corresponding to the connective contacts in each row, row test contacts, one associated with each row, a spindle carrying wipers adapted to co-opcrate with the connective terminals, the individual test contacts and the row test contacts respectively, and circuit connections from the line relays to the individual and row test contacts, whereby the switch may test and find a calling line by testing the row contacts to identify the row and the individual contacts in the row to identity the line.

12. In a telephone exchange system, line circuits, line relays therefor, 21. primary selector switch containing connective terminals in rows connected to the line circuits, individual test contacts corresponding to the connective contacts in each row, row test contacts, one associated with each row, a spindle carrying wipers adapted to co-operate with the connective terminals, the individual test contacts and the row test contacts respectively, and circuit connections from the line relays to the individual and row test contacts, together with a starting circuit for the switch, adapted to be closed by said line relays, whereby a call over any of the lines having terminals in the switch will start the same, and direct the switch to the calling line by successive testing of the row and individual contacts.

13. In a telephone exchange system, a plu rality of line circuits, a selector switch containing terminals for said lines, actuating means for the switch responsive to current in the lines, a testing terminal "for the switch and co-operating line testing terminals therein with means operating over a portion only of the line test terminals to change their potential in response to calls over the corresponding lines, and means controlling the switch actuating means to direct the testing terminal of the switch to the individual test terminal of a calling line.

14;. A telephone system including an operators link circuit, an answering and a calling supervisory signal for said link circuit, a subscriber-controlled answering supervisory relay, a subscriber-controlled calling supervisory relay, circuits for said answering and calling supervisory signals controlled by said answering supervisory relay, and a second circuit for said calling supervisory signal controlled by said calling snpervisory relay in response to a control exercised at the called substation.

15. A link circuit including a subscribercontrolled answering supervisory relay and a subscriber-controlled alling supervis n' relay, a pair of supervisory signals for said link circuit, circuits for said signals controlled by said answering SUPGLVlSOIfJ relay, and a second circuit for one of said supervisory signals controlled by said calling supervisory relay in response to a control exercised at the called substation.

16. A telephone system including a calling subscribers line and a called subscribers line, a link circuitfor connecting said lines in conversational circuit, a calling supervisory signal for said link circuit, a relay controlled by the calling subscriber tor closing an operating circuit for said supervisory signal, means for opening said circuit, and a relay controlled by the called subscriber for closing a second circuit for said supervisory signal.

17. In a telephone system, thecombination with a calling subscribers line, of it called subscribers line, a link circuit for interconnecting the lines, a supervisory signal for said link circuit, means in said link circuit responsive to the joint control o1 apparatus on the calling and called subscribers lines to display said signal, and means operative under the joint control of apparatus in the calling and called subscribers lines for con tinuing the display of said signal independently of the apparatus on one of said subscribers lines.

18. In a telephone system, the combination with a calling subscribers line, of a called subseribers line, a link circuit for interconnecting the lines, a supervisory signal for said link circuit, means in said link circuit responsive to the joint control of apparatus 10 on the calling and called subscribers lines to display said signal, means operative under the joint control of apparatus in the calling and called subscribers lines for continuing the display of said signal independently of the apparatus on one of said subscribers lines, and means responsive to disassociation of the said link circuit With one of said lines to retire the said signal.

In testimony whereof I affix my signature.

EDWARD E. CLEMENT. 

